This invention relates to electronic components having actively controlled circuit elements.
The interconnected electronic components that form many electronic circuits include simple, passive elements, like resistors and capacitors, and more complex actively controlled circuit elements that provide logic and control functions. One example of an actively controlled circuit element is a MOSFET, which can he controlled to perform a switching function (e.g., turned on and off) or controlled in a linear fashion (e.g., the voltage across the MOSFET and/or the current flowing in the MOSFET are controlled over a continuous range of values).
The elements of an electronic component may be formed as regions of material on a substrate as part of an integrated circuit. Or the elements may be commercially available discrete devices (both passive and active) mounted on a circuit board using either conventional soldered leads or surface mounted contact pads.
The resulting electronic components may be packaged in housings or cases that have terminals for making electrical connection to electronic circuits. The terminals of the components can be in the form of leads or surface mounting contact pads.
Micro-lead packaging (MLP) techniques can be used to house integrated circuits and discrete devices in tiny, inexpensive electronic packages that are not much larger than the devices within them and that are easily mounted on circuit boards. Heat can easily and economically be removed from power-dissipating devices that are packaged in MLP packages (see, e.g., U.S. patent application Ser. No. 09/643,159, “Power Converter Assembly”, filed Aug. 21, 2000, incorporated by reference).
Some electronic components can be thought of as serving secondary or service functions for other, primary circuits. For example, a power converter circuit may be considered a primary circuit while a ripple filter component connected to the output of the converter may be viewed as providing a secondary or service function.
Sometimes the service functions are provided by including them directly in the primary circuit. In other cases, when the primary circuits are sold as commercial products without inclusion of the service functions, the service functions may be provided by components that are sold and mounted separately.
For example, a commercially available DC-to-DC power converter will typically include ripple filtering circuitry. However, certain applications require very low ripple, and the additional filtering requirements may be met by providing an add-on commercial product that is connected to the output terminal of the converter. One example of such a secondary product is the VI-RAM Ripple Attenuator Module (“RAM”) available from Vicor Corporation of Andover, Mass., which serves as an active ripple filter at the output of a switching power converter, such as the VI-200 and VI-J00 families of converters sold by Vicor. The filter function of the RAM is provided by a combination of a linear MOSFET element connected between the output of the power converter and the load and an integrated circuit that actively controls the MOSFET to cancel the ripple at the output of the power converter as a way of reducing ripple at the load.